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California Regional Water Qualitypontrol Board - <br /> --, <br /> Central Valley Region f <br /> Steven T.Butler,Chair <br /> Winston H.Hickox Gray Davis <br /> Secretaryfor Sacramento Main Office ; I Governor <br /> Environmental Internet Address: http://www.swrcb.ca.gov/—rwgcb5 <br /> Protection 3443 Routier Road,Suite A,Sacramento,California 95827-3003 <br /> Phone(916)255-3000•FAX(916)255-3015 <br /> 14 October 1999 <br /> Ms. Nancy Bishop <br /> Western Farm Service <br /> 3650 Mt. Diablo Blvd., Suite 260 <br /> Lafayette, CA 94549 <br /> CONDITIONAL APPROVAL OF TREATMENT S YS TEM DESIGN S UMMAR Y, REVIEW OF <br /> QUARTERLYMONITORING REPORT, CAPTURE ZONE ANALYSIS, WESTERN FARM <br /> SERVICE, VERNALIS, SAN JOA QUIN COUNTY <br /> Thank you for submitting the 24 September 1999 Extraction and Treatment System Design Summary <br /> and System Schematics (Design Summary) which describes the carbon adsorption treatment system for <br /> groundwater at the Western Farm Service facility in Vernalis (WFS). This letter provides my comments <br /> on the treatment system and the 28 January 1999 Results of March 1999 Groundwater Monitoring. <br /> Results of March 1999 Groundwater Monitoring <br /> Please abbreviate 1,2-dichloropropane 1,2-DCP instead of 1,2-D as the groundwater monitoring report <br /> shows. There are many compounds that begin with 1,2-D, and I will be able to recognize the referenced <br /> constituent more readily with the longer abbreviation. <br /> Figures 4 and 5 display groundwater elevations and concentrations of nitrate, 1,2-DCP and <br /> dibromochloropropane (DBCP)together on one page. The graphics make it easy to assess that <br /> groundwater elevation is correlated with 1,2-DCP and DBCP concentrations. <br /> Extraction and Treatment System Design <br /> The Design Summary states that the carbon treatment system is designed to remove pesticides and <br /> fumigants from groundwater before the water is used as makeup water in the fertilizer mix plant; the <br /> treated water will be stored in a 40,000 gallon make-up water tank from which the fertilizer mix plant <br /> will draw water as needed. Transducers have been provided that will regulate the extraction pump to <br /> maintain a water volume in the make-up tank between 20,000 and 40,000 gallons and turn the pump off <br /> if system pressure increases above 15 psi, or if the extraction well becomes dewatered. Even though <br /> there is a high-water switch to turn the pump off when the tank is full, WFS should install a backup <br /> system to disable the pump in case the high-water shutoff switch fails. <br /> The Design Summary proposes to take samples for pesticide analyses before and after each carbon unit <br /> weekly for the first two weeks, then monthly thereafter. If a constituent is detected in these initial <br /> weeks, then weekly samples will continue until the constituents are below detection limits. However, if <br /> there is a constituent breakthrough in this early period, a problem would not be noticed until the <br /> California Environmental Protection Agency <br /> �a Recycled Paper <br />